Dear Nabhan: The corrosion of duplex and 316SS in desalianation service could conceivable be due to either chlorides or bacteria (MIC). The pitted appearance can be similar although some people report subtle differences for MIC pitting. You need to conduct a proper failure analysis, if practical, and look at those things that can distinguish between pure chloride pitting and pitting from MIC. Things like taking water samples and testing for bacteria should be done, analyzing deposits, checking the oxygen content of the water, the flow velocities, all might provide some clues. Hope this helps! David Hendrix The Hendrix Group Inc.